KR20130104337A - Apparatus and method for allocating resource in multi-beam satellite communication - Google Patents

Abstract

PURPOSE: A resource allocation apparatus in multi beam satellite communication system and a method thereof are provided to maximize the efficiency of limited satellite resource usage under the assumption that the Power Flux Density (PFD) of each spot beam is equal. CONSTITUTION: A reception unit (11) receives traffic demands of a plurality of beams and the channel state information of a plurality of the beams. An activated beam selection unit (130) selects at least some activated beams based on each of the traffic demands of a plurality of the beams and each channel state information of a plurality of the beams. A resource allocation control unit (140) allocates a communication capacity to each activated beam which makes a PFD level of each of a plurality of the beams equal. The resource allocation control unit determines a bandwidth of each activated beam which minimizes the difference between the traffic demand of each activated beam and the communication capacity of each activated beam which is capable of being allocated. [Reference numerals] (110) Reception unit; (120) Beam allocation control unit; (130) Activated beam selection unit; (140) Resource allocation control unit

Description

Apparatus and method for allocating resources in multi-beam satellite communication system {APPARATUS AND METHOD FOR ALLOCATING RESOURCE IN MULTI-BEAM SATELLITE COMMUNICATION}

The present invention relates to an apparatus and method for allocating resources in a multi-beam satellite communication system. Specifically, in the multi-beam satellite communication system, an activation beam is selected under the assumption that the power flux density of each beam is kept constant. An apparatus and method for allocating band resources.

In a satellite communication system, the radio waves emitted by the satellite to the ground are called beams, and the surface that belongs to the beam is called a cell. A single beam satellite communication system uses one beam and a multiple beam using two or more different spot beams. There is a (multi-beam) satellite communication system.

In a multi-beam satellite communication system, a service area is divided into cells by a multi-spot beam, and a user terminal may form a communication link with a satellite through a beam to which the user belongs and may receive a service through the communication link.

In the multi-beam satellite system, it is possible to dynamically allocate limited satellite resources such as power, band, or spot beam in consideration of the traffic volume and channel conditions of each spot beam, and thus increase the total system capacity by constructing a flexible system. Can be.

Currently, the International Telecommunication Union (ITU) regulates power flux density (PFD) levels for signals transmitted from satellites to the ground, which are adjacent spot beams or other terrestrial reception and communications. It is a requirement that must be considered when designing a satellite communication system to limit the effects of interference on a facility.

Therefore, in order to solve the problem of large fluctuations in the interference level between adjacent beams that may occur in the dynamic resource allocation scheme for the multi-beam satellite system, the PFD is kept constant so that the interference level of each spot beam can be fixed. In order to increase the total system capacity, there is a need for a method for maximizing the utilization efficiency of limited satellite resources.

An object of the present invention is to provide an apparatus and method for allocating resources capable of maximizing the utilization efficiency of limited satellite resources under the assumption that the PFD of each spot beam is constant.

According to an embodiment of the present invention, a method for allocating satellite resources by a satellite in a satellite communication system using multiple beams is provided. The resource allocation method may include selecting at least a portion of an activation beam using a traffic demand of each beam and channel state information of each beam among a plurality of beams having a traffic demand, the traffic requirement of the activation beam and the channel of the activation beam. Determining a bandwidth of the activation beam using state information, and allocating a communication capacity of the activation beam from the bandwidth of the activation beam.

The resource allocation method may further include determining transmission power of the activation beam such that a power flux density (PFD) level of the plurality of beams maintains a set value.

The determining of the bandwidth may include determining a bandwidth of each activation beam such that a difference between the traffic demand of each activation beam and the assignable communication capacity of each activation beam is minimized.

The resource allocation method may further include receiving a traffic requirement of each beam and channel state information of each beam from a satellite gateway.

이고, 상기 Ti는 i번째 빔의 트래픽 요구량이고, αi는 상기 i번째 빔의 채널 상태 정보이며, 상기 ρ는 i번째 빔의 PFD를 나타낼 수 있다. The step of selecting the activation beam includes selecting as the activation beam a predetermined number of beams having a larger value among the values calculated by the calculation equation for each beam, wherein the calculation equation is

, Ti is the traffic requirement of the i-th beam, αi is the channel state information of the i-th beam, and ρ may represent the PFD of the i-th beam.

According to another embodiment of the present invention, an apparatus for allocating satellite resources in a satellite communication system using multiple beams is provided. The apparatus for allocating a resource may include a receiver configured to receive traffic demands of a plurality of beams and channel state information of the plurality of beams, and an activation beam for selecting at least some of the activation beams using the traffic demands of each beam and the channel state information of each beam. A selection unit and a resource allocation control unit for allocating communication capacity to each active beam such that the power flux density (PFD) levels of the beams have the same set value.

The resource allocation controller may determine a bandwidth for minimizing the difference between the traffic demand of each activation beam and the assignable communication capacity of each activation beam as the bandwidth of each activation beam.

The resource allocation controller may adjust the transmission power of each activation beam by using the bandwidth of each activation beam so that the PFD level of each beam has the set value.

The resource allocation controller may calculate a communication capacity for each activation beam by using the bandwidth of each activation beam and the channel state information of each activation beam.

The activation beam selector may select the activation beam in consideration of the same PFD level of each beam.

According to an embodiment of the present invention, in a multi-beam satellite communication system, adjacent beams or other grounds are made constant by maintaining a constant PFD per beam for a problem in which the interference level between adjacent beams that may occur in the dynamic resource allocation scheme may vary widely. It can reduce the influence of interference on communication facilities, and make the design of multi-beam satellite communication systems easier.

1 is a diagram illustrating a multi-beam satellite communication system according to an exemplary embodiment of the present invention.
2 is a flowchart illustrating a resource allocation method in a satellite according to an embodiment of the present invention.
3 is a diagram schematically illustrating an apparatus for allocating satellite resources according to an exemplary embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification and claims, when a section is referred to as "including " an element, it is understood that it does not exclude other elements, but may include other elements, unless specifically stated otherwise.

Now, a resource allocation apparatus and method in a multi-beam satellite communication system according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating a multi-beam satellite communication system according to an exemplary embodiment of the present invention.

Referring to FIG. 1, a multi-beam satellite communication system includes a satellite 10 and a satellite gateway 20, and communicates with a user terminal 30.

The satellite 10 relays communication between the satellite gateway 20 and the user terminal 30 and communication between the user terminal 30.

Satellite 10 uses multiple beams. Radio waves emitted by the satellite 10 to the earth's surface are called beams, and the beam area is called a cell. The service area is composed of several cells by the multiple beams of the satellite 10, and the user terminal 30 forms a communication link with the satellite 10 through the beam to which the user belongs.

The satellite 10 forms a beam pattern with a beam width that is narrow enough to ignore inter-beam interference. There may be various beams in the satellite 10. The beam according to the embodiment of the present invention may be a spot beam.

The satellite 10 communicates with the user terminal 30 through the activation beam by selecting an activation beam from among multiple beams in which traffic has been generated for communication with the user terminal 30 and allocating satellite radio resources to the selected activation beam. .

The satellite 10 dynamically allocates radio resources for each packet transmission in consideration of resource usage and interference in different beams. In particular, the satellite 10 maintains a constant power flux density (PFD) level of each beam so that the interference level between adjacent beams is fixed, and the channel state and traffic demand of each beam in a state where the PFD level of each beam is constant. Reflecting this, selects an activation beam and allocates a radio resource to the selected activation beam.

The satellite gateway 20 relays between the satellite 10 and another wireless communication network, such as a plurality of terrestrial networks or the Internet. In particular, the satellite gateway 20 collects the traffic demand of each beam and the signal attenuation according to the channel state of each beam, and transmits them to the satellite 10.

The satellite gateway 20 may perform the same function and role as the base station in the terrestrial network. Accordingly, the user terminal 30 having the traffic transmits its information to the satellite gateway 20, through which the satellite gateway 20 can collect the amount of signal attenuation according to the traffic demand of each beam and the channel state of each beam. have.

The user terminal 30 may receive a communication service through the satellite 10 by forming a communication link with the satellite 10 through a beam corresponding to the cell where the user is located.

2 and 3 for optimal resource allocation in the physical layer under the assumption that reliable transmission such as a compensation function for distortion due to delay in a transport layer protocol is possible in a multi-beam satellite communication system. It demonstrates with reference.

2 is a flowchart illustrating a resource allocation method in a satellite according to an embodiment of the present invention.

Referring to FIG. 2, the satellite 10 allocates multiple beams (S200). When the number of allocated beams is N, the number of active beams which actually allocates resources among N multiple beams becomes N or less.

Each beam may generate a traffic demand by the user terminal 10 belonging to each beam. Each beam has a traffic demand by the user terminal 10 belonging to each beam and a signal attenuation amount according to the channel state of each beam. The satellite gateway 20 collects the traffic demand of each beam and the signal attenuation according to the channel state of each beam, and transmits them to the satellite 10.

The satellite 10 receives the traffic demand of each beam and the signal attenuation according to the channel state of each beam from the satellite gateway 20 (S210). The satellite gateway 20 collects the traffic demand of each beam and the signal attenuation according to the channel state of each beam, and transmits them to the satellite 10.

The satellite 10 selects an activation beam in consideration of the traffic demand of each beam and the signal attenuation amount according to the channel state of each beam (S220).

The satellite 10 determines a beam band for the selected activation beam (S230), and allocates a communication capacity for the activation beam using the determined beam band (S240).

Next, the satellite 10 determines transmission power of each activation beam so that the activation beam has a set PFD level (S250), and controls each activation beam to have the determined transmission power.

Next, a method of determining the beam band of the activation beam, allocating communication capacity, and determining transmission power in the satellite 10 will be described in detail.

Shannon communication capacity for the band-limited i-th beam may be represented by Equation 1 below.

[Equation 1]

는 i번째 빔의 채널 상태에 따른 신호 감쇠량을 나타내며, ρ는 PFD를 나타내며 P_i/W_iN₀에 의해 구해진다. ρ는 각 빔 당 동일한 PFD 레벨을 갖는다는 가정 하에 하나의 상수가 된다. PFD 레벨은 미리 정해져 있으며 인접 빔 간의 간섭 레벨이 임계 값 이하가 되도록 하는 레벨일 수 있다. P_i와 N₀는 각각 빔의 송신 전력 및 잡음 전력을 나타내고, W_i는 각 빔에 서로 다른 통신 용량을 할당하기 위해 조정되는 대역 자원을 나타낸다. In Equation 1,

Denotes the amount of signal attenuation according to the channel state of the i-th beam, ρ denotes PFD, and is obtained by P _i / W _i N ₀ . ρ becomes one constant on the assumption that each beam has the same PFD level. The PFD level is predetermined and may be a level such that an interference level between adjacent beams is equal to or less than a threshold value. P _i and N ₀ represent the transmit power and noise power of the beam, respectively, and W _i represents the band resource adjusted to allocate different communication capacities to each beam.

According to an embodiment of the present invention, the satellite 10 allocates beamband resources in consideration of traffic requirements and channel conditions of each beam to maximize the utilization of resources so that the balance between fairness and total system capacity among users ( offer a reasonable solution to the trade-off problem. To this end, the satellite 10 aims to match as much as possible the communication capacity C _i and the traffic demand T _i . That is, the satellite 10 uses a cost function to obtain the minimum value of the general function for the difference between {C _i } and {T _i } for all cells for beam band allocation. The cost function is shown in Equation 2.

&Quot; (2) "

In general, the allocation of satellite resources is very limited compared to the signal demands of users. Therefore, the band allocated to the beam cannot be assigned a value larger than the desired signal demand of the beam. This constraint is shown in equation (3).

In addition, the total sum of the bands W _i allocated to each beam cannot exceed the _total band W _total allocable by the satellite 10. This constraint is shown in equation (4).

The satellite 10 derives an optimal resource allocation scheme related to communication capacity and bandwidth efficiency in consideration of Equations 3 and 4 below.

&Quot; (3) "

&Quot; (4) "

In order to solve the convex optimization problem in which constraints such as Equations 3 and 4 exist, the optimized beam bandwidth based on the cost function of Equation 2 and the constraints of Equations 3 and 4 Is solved by solving a Lagrange function as shown in Equation 5.

&Quot; (5) "

Here, Λ is a Lagrange multiplier and is determined according to the _total band W _total allocable by the satellite 10. If Λ always has a value greater than 0, it means that the constraint of Equation 3 is satisfied.

The relationship of Equation 6 can be obtained from Equation 5 by Kuhn-Tucker definition.

&Quot; (6) "

Therefore, by dividing Equation 5 with respect to W _i and applying Equation 6, an optimal beamband allocation equation for the traffic demand of each beam can be obtained in the multi-beam satellite communication system. The optimal beamband allocation equation for the traffic demand of each beam may be as shown in Equation (7).

[Equation 7]

In equation (7), b1, b2, b3 and b4 are constants and are the same as in equation (8).

[Equation 8]

,

,

,

,

,

,

The satellite 10 can obtain an optimal beam bandwidth W _i that minimizes the difference between the traffic demand of each beam and the assignable communication capacity by using the beam band allocation equation (7).

Beam bandwidth W _i is the ground satellite 10 is obtained, and calculating the communication capacity C _i on the basis of equation (3), calculates a communication capacity C _i is to comply with a cost function of Equation (2).

When the beam bandwidth W _i is obtained, the satellite 10 adjusts the transmission power P _i of the beam, so that ρ has a constant value at the set level.

In the multi-beam satellite communication system, each beam is also an important satellite resource, and a method of selecting an activation beam based on a beamband allocation scheme considering the same PFD for each beam will be described in detail.

The satellite 10 further considers the constraint of Equation 9 to select an activation beam. Equation 9 means that a non-zero band should be allocated only to an activation beam selected for resource allocation.

&Quot; (9) "

-W _{i ≤ 0}

In the minimization problem to which the constraint function of Equation 9 is added, Equation 9 may be derived from Equation 5 in which Lagrange function is applied to find an optimization solution for the activation beam selection.

&Quot; (10) "

In Equation 10, v _i is an added Lagrangian coefficient, which is determined by the constraint of Equation 9.

In the same manner as in Equations 6 and 7 described above, Equation 11 may be derived by partially dividing Equation 10 with respect to W _i .

&Quot; (11) "

Using the Coon-Tucker definition, equations (12) and (13) can be defined.

&Quot; (12) "

V _i = 0 when W _i > 0

&Quot; (13) "

V _j ≥0 when W _j = 0

First, assuming that the optimal beam bandwidth W _i ^* is greater than zero (W _i ^* > 0), Equation 14 is obtained according to Equation 12 and Lagrange function theory.

&Quot; (14) "

v _i = 0,

Therefore, equation (15) can be derived from equation (11) and equation (14).

&Quot; (15) "

The inequality relation of Equation 15 is established by the concavity characteristic of the communication capacity C _i .

Next, assuming an optimal case when W _j is 0 with respect to the j th beam, Equation 16 is obtained according to Equation 13 and Lagrange function theory.

&Quot; (16) "

v _j ≥0,

Therefore, Equation 17 may be derived from Equations 11 and 16.

&Quot; (17) "

By comparing each right side with respect to Λ, which is a common factor between Equations 15 and 17, the satellite 10 generates a predetermined number of activation beams in order of having the largest value of Equation 18 for each beam having a traffic demand. Choose.

&Quot; (18) "

As such, the satellite 10 selects a set number of activation beams from among multiple beams based on Equation 18. In this way, beams that degrade the overall performance of the system are excluded from service, and thus the system total throughput can be improved.

3 is a diagram schematically illustrating an apparatus for allocating satellite resources according to an exemplary embodiment of the present invention.

Referring to FIG. 3, the resource allocation apparatus 100 of the satellite 10 includes a receiver 110, a beam allocator 120, an active beam selector 130, and a resource allocation controller 140.

The receiver 110 receives the traffic demand of each beam and the signal attenuation according to the channel state of each beam from the satellite gateway 20.

The beam allocator 120 allocates multiple beams.

The activation beam selector 130 selects the activation beam in consideration of the traffic demand of each beam and the signal attenuation amount according to the channel state of each beam among the multiple beams. In particular, the activation beam selector 130 selects a predetermined number of activation beams in order of having the largest value for each beam having a traffic demand based on Equation (18).

The resource allocation control unit 140 determines an optimal beam band for the activation beam, and allocates a communication capacity for the activation beam using the determined beam band. In addition, the resource allocation control unit 140 determines the transmission power of each activation beam so that each activation beam has the same PFD level, and controls the transmission power of each activation beam.

In particular, the resource allocation control unit 140 determines an optimal beam band for the traffic demand of the activation beam based on Equation 7, and allocates the communication capacity of the activation beam using the beam band determined based on Equation 3. In addition, the resource allocation controller 140 may determine the transmission power of each activation beam such that each activation beam has the same PFD level. Since the PFD level is fixed, the transmit power of the activation beam can be determined from the equation ρ = P _i / W _i N ₀ .

An embodiment of the present invention is not implemented only through the above-described apparatus and / or method, but may be implemented through a program for realizing a function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded. Such an implementation can be easily implemented by those skilled in the art to which the present invention pertains based on the description of the above-described embodiments.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

Claims (14)

In a satellite communication system using multiple beams, a satellite allocates satellite resources,
Selecting at least some of the active beams from the plurality of beams having the traffic demands using the traffic demands of each beam and the channel state information of each beam,
Determining a bandwidth of the activation beam using the traffic demand of the activation beam and channel state information of the activation beam; and
Allocating the communication capacity of the activation beam from the bandwidth of the activation beam
/ RTI > In claim 1,
Determining transmit power of the activation beam such that a power flux density (PFD) level of the plurality of beams maintains a set value;
Resource allocation method further comprising. In claim 1,
Determining the bandwidth,
Determining a bandwidth of each activation beam such that a difference between the traffic demand of each activation beam and the assignable communication capacity of each activation beam is minimized. In claim 1,
Receiving traffic demand of each beam and channel state information of each beam from a satellite gateway
Resource allocation method further comprising. In claim 1,
The channel state information includes a signal attenuation amount according to the channel state. In claim 1,
Selecting the activation beam,
Selecting the set number of beams having a larger value among the values calculated by the formula for each beam as the activation beam,
The above formula is

ego,
Wherein Ti is a traffic requirement of the i-th beam, αi is channel state information of the i-th beam, and ρ represents a PFD of the i-th beam. The method of claim 6,
The PFD level of the plurality of beams has the same value. An apparatus for allocating satellite resources in a satellite communication system using multiple beams,
A receiver for receiving traffic demands of a plurality of beams and channel state information of the plurality of beams;
An activation beam selector for selecting at least some activation beams by using the traffic demand of each beam and the channel state information of each beam, and
Resource allocation control unit for allocating communication capacity to each active beam so that the power flux density (PFD) level of each beam has the same set value
And a resource allocation unit. 9. The method of claim 8,
And the resource allocation controller determines a bandwidth for minimizing a difference between the traffic demand of each activation beam and the assignable communication capacity of each activation beam as the bandwidth of each activation beam. The method of claim 9,
The resource allocation controller adjusts the transmission power of each activation beam by using the bandwidth of each activation beam so that the PFD level of each beam has the set value. The method of claim 9,
The resource allocation controller calculates a communication capacity for each of the activation beams by using the bandwidth of each activation beam and the channel state information of each activation beam. 9. The method of claim 8,
The activation beam selecting unit selects the activation beam in consideration of the same PFD level of each beam. The method of claim 12,
The activation beam selecting unit selects a predetermined number of beams having a large value among the values calculated by a calculation formula for each beam as the activation beam,
The above formula is

ego,
Wherein Ti is a traffic requirement of the i-th beam, αi is channel state information of the i-th beam, and ρ represents a PFD level of the i-th beam. 9. The method of claim 8,
The channel state information includes a signal attenuation amount according to the channel state.

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